Roman Khassraf | 059bab9 | 2015-05-20 12:49:46 +0200 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 2008 Free Software Foundation, Inc. |
| 3 | * |
| 4 | * This software is distributed under the terms of the GNU Public License. |
| 5 | * See the COPYING file in the main directory for details. |
| 6 | |
| 7 | This program is free software: you can redistribute it and/or modify |
| 8 | it under the terms of the GNU General Public License as published by |
| 9 | the Free Software Foundation, either version 3 of the License, or |
| 10 | (at your option) any later version. |
| 11 | |
| 12 | This program is distributed in the hope that it will be useful, |
| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | GNU General Public License for more details. |
| 16 | |
| 17 | You should have received a copy of the GNU General Public License |
| 18 | along with this program. If not, see <http://www.gnu.org/licenses/>. |
| 19 | |
| 20 | */ |
| 21 | |
| 22 | |
| 23 | |
| 24 | |
| 25 | #include "BitVector.h" |
| 26 | #include <iostream> |
| 27 | |
| 28 | using namespace std; |
| 29 | |
| 30 | |
| 31 | /** |
| 32 | Apply a Galois polymonial to a binary seqeunce. |
| 33 | @param val The input sequence. |
| 34 | @param poly The polynomial. |
| 35 | @param order The order of the polynomial. |
| 36 | @return Single-bit result. |
| 37 | */ |
| 38 | unsigned applyPoly(uint64_t val, uint64_t poly, unsigned order) |
| 39 | { |
| 40 | uint64_t prod = val & poly; |
| 41 | unsigned sum = prod; |
| 42 | for (unsigned i=1; i<order; i++) sum ^= prod>>i; |
| 43 | return sum & 0x01; |
| 44 | } |
| 45 | |
| 46 | |
| 47 | |
| 48 | |
| 49 | |
| 50 | |
| 51 | BitVector::BitVector(const char *valString) |
| 52 | :Vector<char>(strlen(valString)) |
| 53 | { |
| 54 | uint32_t accum = 0; |
| 55 | for (size_t i=0; i<size(); i++) { |
| 56 | accum <<= 1; |
| 57 | if (valString[i]=='1') accum |= 0x01; |
| 58 | mStart[i] = accum; |
| 59 | } |
| 60 | } |
| 61 | |
| 62 | |
| 63 | |
| 64 | |
| 65 | |
| 66 | uint64_t BitVector::peekField(size_t readIndex, unsigned length) const |
| 67 | { |
| 68 | uint64_t accum = 0; |
| 69 | char *dp = mStart + readIndex; |
| 70 | assert(dp+length <= mEnd); |
| 71 | for (unsigned i=0; i<length; i++) { |
| 72 | accum = (accum<<1) | ((*dp++) & 0x01); |
| 73 | } |
| 74 | return accum; |
| 75 | } |
| 76 | |
| 77 | |
| 78 | uint64_t BitVector::readField(size_t& readIndex, unsigned length) const |
| 79 | { |
| 80 | const uint64_t retVal = peekField(readIndex,length); |
| 81 | readIndex += length; |
| 82 | return retVal; |
| 83 | } |
| 84 | |
| 85 | |
| 86 | void BitVector::fillField(size_t writeIndex, uint64_t value, unsigned length) |
| 87 | { |
| 88 | char *dpBase = mStart + writeIndex; |
| 89 | char *dp = dpBase + length - 1; |
| 90 | assert(dp < mEnd); |
| 91 | while (dp>=dpBase) { |
| 92 | *dp-- = value & 0x01; |
| 93 | value >>= 1; |
| 94 | } |
| 95 | } |
| 96 | |
| 97 | void BitVector::writeField(size_t& writeIndex, uint64_t value, unsigned length) |
| 98 | { |
| 99 | fillField(writeIndex,value,length); |
| 100 | writeIndex += length; |
| 101 | } |
| 102 | |
| 103 | |
| 104 | void BitVector::invert() |
| 105 | { |
| 106 | for (size_t i=0; i<size(); i++) { |
| 107 | mStart[i] = ~mStart[i]; |
| 108 | } |
| 109 | } |
| 110 | |
| 111 | |
| 112 | |
| 113 | |
| 114 | void BitVector::reverse8() |
| 115 | { |
| 116 | assert(size()>=8); |
| 117 | |
| 118 | char tmp0 = mStart[0]; |
| 119 | mStart[0] = mStart[7]; |
| 120 | mStart[7] = tmp0; |
| 121 | |
| 122 | char tmp1 = mStart[1]; |
| 123 | mStart[1] = mStart[6]; |
| 124 | mStart[6] = tmp1; |
| 125 | |
| 126 | char tmp2 = mStart[2]; |
| 127 | mStart[2] = mStart[5]; |
| 128 | mStart[5] = tmp2; |
| 129 | |
| 130 | char tmp3 = mStart[3]; |
| 131 | mStart[3] = mStart[4]; |
| 132 | mStart[4] = tmp3; |
| 133 | } |
| 134 | |
| 135 | |
| 136 | |
| 137 | void BitVector::LSB8MSB() |
| 138 | { |
| 139 | size_t size8 = 8*(size()/8); |
| 140 | size_t iTop = size8 - 8; |
| 141 | for (size_t i=0; i<=iTop; i+=8) segment(i,8).reverse8(); |
| 142 | } |
| 143 | |
| 144 | |
| 145 | |
| 146 | uint64_t BitVector::syndrome(Generator& gen) const |
| 147 | { |
| 148 | gen.clear(); |
| 149 | const char *dp = mStart; |
| 150 | while (dp<mEnd) gen.syndromeShift(*dp++); |
| 151 | return gen.state(); |
| 152 | } |
| 153 | |
| 154 | |
| 155 | uint64_t BitVector::parity(Generator& gen) const |
| 156 | { |
| 157 | gen.clear(); |
| 158 | const char *dp = mStart; |
| 159 | while (dp<mEnd) gen.encoderShift(*dp++); |
| 160 | return gen.state(); |
| 161 | } |
| 162 | |
| 163 | |
| 164 | void BitVector::encode(const ViterbiR2O4& coder, BitVector& target) |
| 165 | { |
| 166 | size_t sz = size(); |
| 167 | assert(sz*coder.iRate() == target.size()); |
| 168 | |
| 169 | // Build a "history" array where each element contains the full history. |
| 170 | uint32_t history[sz]; |
| 171 | uint32_t accum = 0; |
| 172 | for (size_t i=0; i<sz; i++) { |
| 173 | accum = (accum<<1) | bit(i); |
| 174 | history[i] = accum; |
| 175 | } |
| 176 | |
| 177 | // Look up histories in the pre-generated state table. |
| 178 | char *op = target.begin(); |
| 179 | for (size_t i=0; i<sz; i++) { |
| 180 | unsigned index = coder.cMask() & history[i]; |
| 181 | for (unsigned g=0; g<coder.iRate(); g++) { |
| 182 | *op++ = coder.stateTable(g,index); |
| 183 | } |
| 184 | } |
| 185 | } |
| 186 | |
| 187 | |
| 188 | |
| 189 | unsigned BitVector::sum() const |
| 190 | { |
| 191 | unsigned sum = 0; |
| 192 | for (size_t i=0; i<size(); i++) sum += mStart[i] & 0x01; |
| 193 | return sum; |
| 194 | } |
| 195 | |
| 196 | |
| 197 | |
| 198 | |
| 199 | void BitVector::map(const unsigned *map, size_t mapSize, BitVector& dest) const |
| 200 | { |
| 201 | for (unsigned i=0; i<mapSize; i++) { |
| 202 | dest.mStart[i] = mStart[map[i]]; |
| 203 | } |
| 204 | } |
| 205 | |
| 206 | |
| 207 | |
| 208 | |
| 209 | void BitVector::unmap(const unsigned *map, size_t mapSize, BitVector& dest) const |
| 210 | { |
| 211 | for (unsigned i=0; i<mapSize; i++) { |
| 212 | dest.mStart[map[i]] = mStart[i]; |
| 213 | } |
| 214 | } |
| 215 | |
| 216 | |
| 217 | |
| 218 | |
| 219 | |
| 220 | |
| 221 | |
| 222 | |
| 223 | |
| 224 | |
| 225 | ostream& operator<<(ostream& os, const BitVector& hv) |
| 226 | { |
| 227 | for (size_t i=0; i<hv.size(); i++) { |
| 228 | if (hv.bit(i)) os << '1'; |
| 229 | else os << '0'; |
| 230 | } |
| 231 | return os; |
| 232 | } |
| 233 | |
| 234 | |
| 235 | |
| 236 | |
| 237 | ViterbiR2O4::ViterbiR2O4() |
| 238 | { |
| 239 | assert(mDeferral < 32); |
| 240 | mCoeffs[0] = 0x019; |
| 241 | mCoeffs[1] = 0x01b; |
| 242 | computeStateTables(0); |
| 243 | computeStateTables(1); |
| 244 | computeGeneratorTable(); |
| 245 | } |
| 246 | |
| 247 | |
| 248 | |
| 249 | |
| 250 | void ViterbiR2O4::initializeStates() |
| 251 | { |
| 252 | for (unsigned i=0; i<mIStates; i++) clear(mSurvivors[i]); |
| 253 | for (unsigned i=0; i<mNumCands; i++) clear(mCandidates[i]); |
| 254 | } |
| 255 | |
| 256 | |
| 257 | |
| 258 | void ViterbiR2O4::computeStateTables(unsigned g) |
| 259 | { |
| 260 | assert(g<mIRate); |
| 261 | for (unsigned state=0; state<mIStates; state++) { |
| 262 | // 0 input |
| 263 | uint32_t inputVal = state<<1; |
| 264 | mStateTable[g][inputVal] = applyPoly(inputVal, mCoeffs[g], mOrder+1); |
| 265 | // 1 input |
| 266 | inputVal |= 1; |
| 267 | mStateTable[g][inputVal] = applyPoly(inputVal, mCoeffs[g], mOrder+1); |
| 268 | } |
| 269 | } |
| 270 | |
| 271 | void ViterbiR2O4::computeGeneratorTable() |
| 272 | { |
| 273 | for (unsigned index=0; index<mIStates*2; index++) { |
| 274 | mGeneratorTable[index] = (mStateTable[0][index]<<1) | mStateTable[1][index]; |
| 275 | } |
| 276 | } |
| 277 | |
| 278 | |
| 279 | |
| 280 | |
| 281 | |
| 282 | |
| 283 | void ViterbiR2O4::branchCandidates() |
| 284 | { |
| 285 | // Branch to generate new input states. |
| 286 | const vCand *sp = mSurvivors; |
| 287 | for (unsigned i=0; i<mNumCands; i+=2) { |
| 288 | // extend and suffix |
| 289 | const uint32_t iState0 = (sp->iState) << 1; // input state for 0 |
| 290 | const uint32_t iState1 = iState0 | 0x01; // input state for 1 |
| 291 | const uint32_t oStateShifted = (sp->oState) << mIRate; // shifted output |
| 292 | const float cost = sp->cost; |
| 293 | sp++; |
| 294 | // 0 input extension |
| 295 | mCandidates[i].cost = cost; |
| 296 | mCandidates[i].oState = oStateShifted | mGeneratorTable[iState0 & mCMask]; |
| 297 | mCandidates[i].iState = iState0; |
| 298 | // 1 input extension |
| 299 | mCandidates[i+1].cost = cost; |
| 300 | mCandidates[i+1].oState = oStateShifted | mGeneratorTable[iState1 & mCMask]; |
| 301 | mCandidates[i+1].iState = iState1; |
| 302 | } |
| 303 | } |
| 304 | |
| 305 | |
| 306 | void ViterbiR2O4::getSoftCostMetrics(const uint32_t inSample, const float *matchCost, const float *mismatchCost) |
| 307 | { |
| 308 | const float *cTab[2] = {matchCost,mismatchCost}; |
| 309 | for (unsigned i=0; i<mNumCands; i++) { |
| 310 | vCand& thisCand = mCandidates[i]; |
| 311 | // We examine input bits 2 at a time for a rate 1/2 coder. |
| 312 | const unsigned mismatched = inSample ^ (thisCand.oState); |
| 313 | thisCand.cost += cTab[mismatched&0x01][1] + cTab[(mismatched>>1)&0x01][0]; |
| 314 | } |
| 315 | } |
| 316 | |
| 317 | |
| 318 | void ViterbiR2O4::pruneCandidates() |
| 319 | { |
| 320 | const vCand* c1 = mCandidates; // 0-prefix |
| 321 | const vCand* c2 = mCandidates + mIStates; // 1-prefix |
| 322 | for (unsigned i=0; i<mIStates; i++) { |
| 323 | if (c1[i].cost < c2[i].cost) mSurvivors[i] = c1[i]; |
| 324 | else mSurvivors[i] = c2[i]; |
| 325 | } |
| 326 | } |
| 327 | |
| 328 | |
| 329 | const ViterbiR2O4::vCand& ViterbiR2O4::minCost() const |
| 330 | { |
| 331 | int minIndex = 0; |
| 332 | float minCost = mSurvivors[0].cost; |
| 333 | for (unsigned i=1; i<mIStates; i++) { |
| 334 | const float thisCost = mSurvivors[i].cost; |
| 335 | if (thisCost>=minCost) continue; |
| 336 | minCost = thisCost; |
| 337 | minIndex=i; |
| 338 | } |
| 339 | return mSurvivors[minIndex]; |
| 340 | } |
| 341 | |
| 342 | |
| 343 | const ViterbiR2O4::vCand& ViterbiR2O4::step(uint32_t inSample, const float *probs, const float *iprobs) |
| 344 | { |
| 345 | branchCandidates(); |
| 346 | getSoftCostMetrics(inSample,probs,iprobs); |
| 347 | pruneCandidates(); |
| 348 | return minCost(); |
| 349 | } |
| 350 | |
| 351 | |
| 352 | uint64_t Parity::syndrome(const BitVector& receivedCodeword) |
| 353 | { |
| 354 | return receivedCodeword.syndrome(*this); |
| 355 | } |
| 356 | |
| 357 | |
| 358 | void Parity::writeParityWord(const BitVector& data, BitVector& parityTarget, bool invert) |
| 359 | { |
| 360 | uint64_t pWord = data.parity(*this); |
| 361 | if (invert) pWord = ~pWord; |
| 362 | parityTarget.fillField(0,pWord,size()); |
| 363 | } |
| 364 | |
| 365 | |
| 366 | |
| 367 | |
| 368 | |
| 369 | |
| 370 | |
| 371 | |
| 372 | |
| 373 | SoftVector::SoftVector(const BitVector& source) |
| 374 | { |
| 375 | resize(source.size()); |
| 376 | for (size_t i=0; i<size(); i++) { |
| 377 | if (source.bit(i)) mStart[i]=1.0F; |
| 378 | else mStart[i]=0.0F; |
| 379 | } |
| 380 | } |
| 381 | |
| 382 | |
| 383 | BitVector SoftVector::sliced() const |
| 384 | { |
| 385 | size_t sz = size(); |
| 386 | BitVector newSig(sz); |
| 387 | for (size_t i=0; i<sz; i++) { |
| 388 | if (mStart[i]>0.5F) newSig[i]=1; |
| 389 | else newSig[i] = 0; |
| 390 | } |
| 391 | return newSig; |
| 392 | } |
| 393 | |
| 394 | |
| 395 | |
| 396 | void SoftVector::decode(ViterbiR2O4 &decoder, BitVector& target) const |
| 397 | { |
| 398 | const size_t sz = size(); |
| 399 | const unsigned deferral = decoder.deferral(); |
| 400 | const size_t ctsz = sz + deferral; |
| 401 | assert(sz <= decoder.iRate()*target.size()); |
| 402 | |
| 403 | // Build a "history" array where each element contains the full history. |
| 404 | uint32_t history[ctsz]; |
| 405 | { |
| 406 | BitVector bits = sliced(); |
| 407 | uint32_t accum = 0; |
| 408 | for (size_t i=0; i<sz; i++) { |
| 409 | accum = (accum<<1) | bits.bit(i); |
| 410 | history[i] = accum; |
| 411 | } |
| 412 | // Repeat last bit at the end. |
| 413 | for (size_t i=sz; i<ctsz; i++) { |
| 414 | accum = (accum<<1) | (accum & 0x01); |
| 415 | history[i] = accum; |
| 416 | } |
| 417 | } |
| 418 | |
| 419 | // Precompute metric tables. |
| 420 | float matchCostTable[ctsz]; |
| 421 | float mismatchCostTable[ctsz]; |
| 422 | { |
| 423 | const float *dp = mStart; |
| 424 | for (size_t i=0; i<sz; i++) { |
| 425 | // pVal is the probability that a bit is correct. |
| 426 | // ipVal is the probability that a bit is correct. |
| 427 | float pVal = dp[i]; |
| 428 | if (pVal>0.5F) pVal = 1.0F-pVal; |
| 429 | float ipVal = 1.0F-pVal; |
| 430 | // This is a cheap approximation to an ideal cost function. |
| 431 | if (pVal<0.01F) pVal = 0.01; |
| 432 | if (ipVal<0.01F) ipVal = 0.01; |
| 433 | matchCostTable[i] = 0.25F/ipVal; |
| 434 | mismatchCostTable[i] = 0.25F/pVal; |
| 435 | } |
| 436 | |
| 437 | // pad end of table with unknowns |
| 438 | for (size_t i=sz; i<ctsz; i++) { |
| 439 | matchCostTable[i] = 0.5F; |
| 440 | mismatchCostTable[i] = 0.5F; |
| 441 | } |
| 442 | } |
| 443 | |
| 444 | { |
| 445 | decoder.initializeStates(); |
| 446 | // Each sample of history[] carries its history. |
| 447 | // So we only have to process every iRate-th sample. |
| 448 | const unsigned step = decoder.iRate(); |
| 449 | // input pointer |
| 450 | const uint32_t *ip = history + step - 1; |
| 451 | // output pointers |
| 452 | char *op = target.begin(); |
| 453 | const char *const opt = target.end(); |
| 454 | // table pointers |
| 455 | const float* match = matchCostTable; |
| 456 | const float* mismatch = mismatchCostTable; |
| 457 | size_t oCount = 0; |
| 458 | while (op<opt) { |
| 459 | // Viterbi algorithm |
| 460 | const ViterbiR2O4::vCand &minCost = decoder.step(*ip, match, mismatch); |
| 461 | ip += step; |
| 462 | match += step; |
| 463 | mismatch += step; |
| 464 | // output |
| 465 | if (oCount>=deferral) *op++ = (minCost.iState >> deferral); |
| 466 | oCount++; |
| 467 | } |
| 468 | } |
| 469 | } |
| 470 | |
| 471 | |
| 472 | |
| 473 | |
| 474 | ostream& operator<<(ostream& os, const SoftVector& sv) |
| 475 | { |
| 476 | for (size_t i=0; i<sv.size(); i++) { |
| 477 | if (sv[i]<0.25) os << "0"; |
| 478 | else if (sv[i]>0.75) os << "1"; |
| 479 | else os << "-"; |
| 480 | } |
| 481 | return os; |
| 482 | } |
| 483 | |
| 484 | |
| 485 | |
| 486 | void BitVector::pack(unsigned char* targ) const |
| 487 | { |
| 488 | // Assumes MSB-first packing. |
| 489 | unsigned bytes = size()/8; |
| 490 | for (unsigned i=0; i<bytes; i++) { |
| 491 | targ[i] = peekField(i*8,8); |
| 492 | } |
| 493 | unsigned whole = bytes*8; |
| 494 | unsigned rem = size() - whole; |
| 495 | if (rem==0) return; |
| 496 | targ[bytes] = peekField(whole,rem) << (8-rem); |
| 497 | } |
| 498 | |
| 499 | |
| 500 | void BitVector::unpack(const unsigned char* src) |
| 501 | { |
| 502 | // Assumes MSB-first packing. |
| 503 | unsigned bytes = size()/8; |
| 504 | for (unsigned i=0; i<bytes; i++) { |
| 505 | fillField(i*8,src[i],8); |
| 506 | } |
| 507 | unsigned whole = bytes*8; |
| 508 | unsigned rem = size() - whole; |
| 509 | if (rem==0) return; |
| 510 | fillField(whole,src[bytes],rem); |
| 511 | } |
| 512 | |
| 513 | // vim: ts=4 sw=4 |